The responsibilities of an ice-breaker are manifold, but a major task is to open channels through ice-fields so merchant ships can pass along. Assisting merchant ships often means that the ice-breaker must be able to turn around within a limited space.
The hull of an ice-breaker shall be designed in such a manner, that broken-off floes are largely pushed out below the iceboundaries of the channel, and do not disturb the propellers and fill the opened channel. The power consumption of the vessel is of course an important point to consider.
There are ice-breakers having a bow portion provided with a downwardly-rearwardly extending enlargement at each longitudinal side, a so called reamer, which determine the effective breadth of the channel, which, due to the reamers will be wider than the breadth of the hull.
Ice-breakers of this type have shown very favourable operational performance, also during severe ice conditions.
It may, however, happen that the vessel will be caught in a wall of ice, and it may also be advantageous to perform narrow turns in connection to the opened channel.